Effect of non-linear interface kinetics on coarsening phenomena

TL;DR

This paper investigates how non-linear interface kinetics influence coarsening behavior in nanocrystalline microstructures, revealing that sub-linear IM rate dependence on curvature leads to unexpectedly stable microstructures.

Contribution

It introduces a modified mean field law for coarsening kinetics accounting for non-linear interface migration rates, supported by molecular dynamics simulations.

Findings

IM rates show sub-linear dependence on curvature

Non-linear kinetics explain stable nanocrystalline microstructures

Modified coarsening law aligns with experimental observations

Abstract

Coarsening kinetics is usually described using a linear gradient approximation for the underlying interface migration (IM) rates, wherein the migration fluxes at the interfaces vary linearly with the driving force. Recent experimental studies have shown that coarsening of nanocrystalline interface microstructures is unexpectedly stable compared to conventional parabolic coarsening kinetics. Here, we show that during early stage coarsening of these microstructures, IM rates can develop a non-linear dependence on the driving force, the mean interface curvature. We derive the modified mean field law for coarsening kinetics. Molecular dynamics simulations of individual grain boundaries reveal a sub-linear curvature dependence of IM rates, suggesting an intrinsic origin for the slow coarsening kinetics observed in polycrystalline metals.